Pediatric obesity is a highly prevalent problem, requiring both treatment and prevention efforts to reduce cardiovascular disease risk and metabolic consequences among affected children and the child population. The efficacy of family-based behavioral pediatric obesity treatment is likely compromised by non-optimal parent and child use of the behavioral skills of food and activity monitoring, contingency management, and environmental control. Participant behavioral skills use (BSU) is among the most potent correlates of adult obesity treatment outcome. However, in pediatric obesity treatment trials, BSU assessment is infrequent, when conducted is often only retrospectively recalled by parent report, has unknown reliability, and is incomplete, mostly assessing only the quality of food monitoring. Poor and incomplete BSU measurement precludes improving behavioral interventions for pediatric obesity. Furthermore, different approaches to help families initiate and sustain BSU during and following treatment have not been tested. This R21 developmental/exploratory proposal, in response to PA-06-298 - Understanding Mechanisms of Health Risk Behavior Change in Children and Adolescents-, aims to investigate 1) prospective relations between BSU measured during and following treatment and change in child weight status, physical activity, and diet, and 2) differences in BSU trajectory between different implementation approaches (prescriptive versus self-directed) during and following treatment. Eighty-two parent-child pairs will be randomly assigned to receive either a prescriptive or self-directed implementation approach to family-based behavioral pediatric obesity treatment. Parent- and interventionist-report of the family's use of each behavioral skill (monitoring, contingency management, environmental control) will be assessed at baseline, at the 5th, 10th, and 15th treatment sessions, at post-treatment and at the 3-month and 6-month follow-ups. A supplemental assessment of use of each skill will also be conducted at these time points. Prospective associations between BSU, measured multiple times and by multiple informant/formats, and change in child weight status (z-BMI) and weight-related behaviors (diet, physical activity) over the course of treatment and throughout follow-up will be examined. This proposal will provide important information about the type of BSU and its measurement that is most related to short- and long-term treatment efficacy, and provide pilot data on the relative efficacy of different implementation approaches to initiate and sustain BSU in pediatric obesity intervention. Pediatric obesity is a growing public health problem in the United States and has negative health, psychosocial, and economic consequences for individuals and the population. This proposal investigates core mechanisms and strategies for improving interventions for childhood overweight.